Method and apparatus for data transmissions in a wireless network

ABSTRACT

A method and apparatus for data transmissions in a wireless network are disclosed. A first device may send a first frame to a second device including information regarding a number of pending data frames to be transmitted from the first device to the second device. The first device receives an acknowledgement frame including a number of approved data frames for transmission from the first device to the second device. The first device then may send a plurality of data frames without performing the contention-based channel access procedure in response to the acknowledgement frame. The first device may send a first frame to a second device for requesting data frames that are pending at the second device. The first device receives an acknowledgement frame including a number of pending and approved data frames. The first device may receive a plurality of data frames in response to the acknowledgement frame.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/425,814, filed Mar. 21, 2012, which claims the benefit of U.S.provisional application No. 61/466,153 filed Mar. 22, 2011, the contentsof which is hereby incorporated by reference herein.

BACKGROUND

The IEEE 802.15 working group has been formed to create wirelesspersonal area network (WPAN) standards. The IEEE 802.15 defines threeclasses of WPANs that are differentiated by data rate, batteryconsumption, quality of service (QoS), and the like. IEEE 802.15.1defines a medium rate WPAN that may handle a variety of applications andhave QoS suitable for voice communications. IEEE 802.15.3 defines a highdata rate WPAN that is suitable for applications that require high QoS.IEEE 802.15.4 defines a low rate WPAN that is intended to serveapplications with low power consumption and cost requirement and withrelaxed needs for data rate and QoS.

SUMMARY

A sender (either a coordinator or a WTRU) may inform a receiver of thenumber of pending data frames, so that the sender may (continuously)transmit data frames without performing a contention-based channelaccess procedure to obtain a transmission opportunity on a channel ofthe network. The data frame transmission may be constrained by thelength of active time interval at the receiver or by the fairnessconsideration among different nodes. The transmissions in accordancewith this scheme may reduce overhead introduced by control commands, forexample, data request command, and may improve transmission latency,energy-efficiency and channel utilization. The embodiments may beimplemented by using several reserved and unused bits in a frame controlsubfield of a medium access control (MAC) header in an MAC frame.

In one example embodiment, a first device may send a first frame to asecond device including information regarding a number of pending dataframes (NPD) to be transmitted from the first device to the seconddevice. The first device receives an acknowledgement frame includinginformation regarding a number of approved data frames (NAD) fortransmission from the first device to the second device. The firstdevice then may send a plurality of data frames without performing thecontention-based channel access procedure in response to theacknowledgement frame.

In another example embodiment, a first device may send a first frame toa second device for requesting data frames that are pending at thesecond device. The first device receives an acknowledgement frameincluding information regarding a number of pending and approved dataframes (NPAD) for transmission to the first device. The first device mayreceive a plurality of data frames in response to the acknowledgementframe. The first frame may include information regarding length ofactive time interval (LATI) of the first device, and the NPAD may bedetermined based on the LATI.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIGS. 2A and 2B show an example WPAN in which one or more disclosedembodiments may be implemented;

FIG. 3 is a signaling diagram of an example process for datatransmission from a WTRU to a coordinator in a WPAN;

FIG. 4 is a signaling diagram of an example process for datatransmission from a coordinator to a WTRU in a WPAN;

FIG. 5 is a signaling diagram of an example process of transmission froma WTRU to a coordinator in accordance with one embodiment;

FIG. 6 shows a general medium access control (MAC) frame format;

FIG. 7 shows a format of the frame control field in the MAC frame ofFIG. 6;

FIG. 8 shows an example MAC frame format for data from a WTRU to acoordinator including number of pending data frames (NPD) in accordancewith one embodiment;

FIG. 9 shows an example MAC frame format for acknowledgement (ACK) froma coordinator to a WTRU including number of approved data frames (NAD)and an ACK request subfield set as clear-to-send (CTS) in accordancewith one embodiment;

FIG. 10 is a signaling diagram of an example process of transmittingdata from a coordinator to a WTRU in accordance with one embodiment;

FIG. 11 shows an example format of a data request frame sent from a WTRUto a coordinator with length of active time interval (LATI) inaccordance with one embodiment;

FIG. 12 shows an example format of an ACK frame transmitted from acoordinator to a WTRU with number of pending and approved data frames(NPAD) and ACK request field set to indicate CTS;

FIG. 13 shows an example format of an ACK frame transmitted from a WTRUto a coordinator in accordance with this embodiment;

FIG. 14 is a signaling diagram of an example process of transmittingdata from a WTRU to a coordinator using a data request andacknowledgement frame (DRACK) in accordance with one embodiment;

FIG. 15 is a signaling diagram of an example process of transmittingdata from a coordinator to a WTRU using a DRACK frame in accordance withone embodiment; and

FIG. 16 shows an example format of the DRACK frame.

DETAILED DESCRIPTION

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the networks 112. By way of example, the base stations 114 a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a HomeNode B, a Home eNode B, a site controller, an access point (AP), awireless router, and the like. While the base stations 114 a, 114 b areeach depicted as a single element, it will be appreciated that the basestations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 106, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 106 and/or the removable memory 132.The non-removable memory 106 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. As noted above, the RAN 104 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 116. The RAN 104 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 104 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 104. TheRAN 104 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 104 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 104 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 104 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

Throughout the disclosure, the terms “continuous transmission” or“transmit continuously” mean that a WTRU or a coordinator may transmit adata packet without performing a contention-based channel accessprocedure to obtain a transmission opportunity on a channel in the WPAN,and each data packet transmission does not necessarily occurcontinuously in time. Hereafter, CSMA/CA will be used as an example ofthe contention-based channel access procedure throughout the disclosure,but any contention-based channel access mechanism may be used.

FIGS. 2A and 2B show an example WPAN in which one or more disclosedembodiments may be implemented. The WPAN comprises several WTRUs 210including a coordinator 220. A WTRU 210 may be a reduced-function device(RFD) or a full-function device (FFD). Two or more WTRUs 210 within anoperating space communicating on the same physical channel constitute aWPAN. The WPAN includes at least one WTRU operating as a coordinator220. A coordinator 220 may provide synchronization services through thetransmission of beacons. Alternatively, the WPAN may operate withoutbeacon. The embodiments disclosed herein are applicable to both cases.

The WPAN may operate in the star topology as shown in FIG. 2A or in thepeer-to-peer topology as shown in FIG. 2B. In the star topology, thecommunication is established between WTRUs 210 and a coordinator 220.The coordinator 220 is the primary controller of the WPAN. Thepeer-to-peer topology may have a coordinator, but any WTRU maycommunicate with any other WTRU as long as they are in range of oneanother. Peer-to-peer topology allows more complex network formations tobe implemented, such as mesh networking topology. A peer-to-peer networkmay be ad hoc, self-organizing, or self-healing. It may allow multiplehops to route messages from any WTRU to another on the network.

FIG. 3 is a signaling diagram of an example process for datatransmission from a WTRU 210 to a coordinator 220 in a WPAN. For thecommunication from a WTRU 210 to a coordinator 220, the WTRU 210transmits a data frame to the coordinator 220 after obtaining atransmission opportunity using a contention-based channel accessprocedure (such as unslotted carrier sense multiple access withcollision avoidance (CSMA-CA)) (302). The coordinator 220 may send anacknowledgement (ACK) frame to the WTRU 210 depending on whether thedata frame requires an ACK (304).

FIG. 4 is a signaling diagram of an example process for datatransmission from a coordinator 220 to a WTRU 210 in a WPAN. For thecommunication from a coordinator 220 to a WTRU 210, a receiver-initiatedprocess is used. The WTRU 210 first sends a data request frame to thecoordinator 220 using unslotted CSMA-CA to check if there is some datapending for the WTRU 210 (402). The coordinator 220 then informs theWTRU 210 whether or not there is a data frame pending for the WTRU 210by sending an ACK to the WTRU 210 (404). On a condition that there is adata frame pending, the coordinator 220 transmits the data frame to theWTRU 210 using unslotted CSMA-CA (406). If requested, the WTRU 210 mayacknowledge the successful reception of the data frame by sending an ACKto the coordinator 220 (408).

FIG. 5 is a signaling diagram of an example process 500 of transmissionfrom a WTRU 210 to a coordinator 220 in accordance with one embodiment.A WTRU 210 sends a data frame to a coordinator 220 after obtaining atransmission opportunity using a contention-based channel accessprocedure (such as unslotted CSMA/CA) (502). The data frame includes aninformation element or field indicating the number of pending dataframes (NPD) at the WTRU 210, (i.e., the number of data frames to betransmitted to the coordinator 220).

The coordinator 220 receives the data frame and extracts the NPDinformation. The coordinator 220 determines how many data frames theWTRU 210 may transmit continuously without using unslotted CSMA-CA,which is referred to as the number of approved data frames (NAD). Thecoordinator 220 then sends an ACK including the NAD to the WTRU 210(504).

The NAD may be equal to or smaller than the NPD. When determining theNAD, the coordinator 220 may consider factors, such as fairness, serviceproperties, the NPD, or the like. For example, if a WTRU always requestsa big NPD, it may starve other WTRUs and cause unfairness among WTRUs ifthe coordinator always grants NAD=NPD for this WTRU. In another casewhere a WTRU generates more useful and time-critical information, thecoordinator may grant more transmission opportunities to such WTRU. Anyalgorithm or policies may be employed for determining the NAD.

After receiving the ACK from the coordinator 220, the WTRU 210 may startto continuously transmit data frames without using unslotted CSMA/CA(506, 510). The channel is reserved until completion of thetransmissions of the NAD data packets unless it is terminated early bythe coordinator. For the data packet transmissions, the WTRU 210 doesnot perform the CSMA/CA procedure to obtain the transmissionopportunity, but may simply start transmissions of the packets. In eachdata frame transmitted, the WTRU 210 may include an NPD for theremaining data packets. The NPD may be further decreased if, forexample, some data frames are dropped, for example, due to timeexpiration.

The coordinator 220 may send an ACK to each data frame received (508,512). The ACK frame may include CTS set to ‘1’ and updated NAD value.Other WTRUs not involved in the continuous packet transmission mayrefrain from accessing the channel by detecting the channel or detectingthe ACK packet with CTS=1.

When all NAD packets have been transmitted and acknowledged, thecoordinator 220 may send an additional ACK with CTS=0 and NAD=0, whichindicates the ending of current continuous transmission cycle with theWTRU 210, which informs other WTRUs of the release of the channel (510).

During the continuous transmission cycle, the coordinator 220 may sendan ACK with CTS=0 (or any other frame) to halt the continuoustransmission before the WTRU 210 completes transmitting all NAD packets,(e.g., if there is a collision).

FIG. 6 shows a general MAC frame format 600. The MAC frame 600 includesa MAC header (MHR) including a frame control field 610. FIG. 7 shows aformat of the frame control field 610 in the MHR. The frame typesubfield 612 indicates the type of the frame, for example, beacon, data,acknowledgement, MAC command, etc. The frame pending subfield 614indicates whether the device sending the frame has additional data tosend to the recipient following the current transfer. The acknowledgmentrequest subfield 616 specifies whether an acknowledgment is requiredfrom the recipient device on receipt of a data or MAC command frame.

FIG. 8 shows an example MAC frame format for data from a WTRU 210 to acoordinator 220 including NPD 810 in accordance with one embodiment. TheNPD 810 may be indicated, for example, by using reserved bits 618 (e.g.,bits 7-9) in a frame control field 610 of the MHR when the WTRU 210sends a data frame to the coordinator 220. When the WTRU 210 starts tosend a data frame, on a condition that there is no more data framepending, the frame pending subfield 614 is set to ‘0’; otherwise, theframe pending subfield 614 is set to ‘1.’ When the frame pendingsubfield 614 is set to ‘1’, (i.e., the WTRU 210 has more data to sendcontinuously without using CSMA-CA in accordance with any embodimentsdisclosed herein), the NPD may be encoded, for example, into thereserved bits 810 (bits 7-9) of the frame control field 610 of the MACframe. Table 1 shows an example encoding of the bits for the NPD (bits7-9 of the frame control field) in accordance with one embodiment. Itshould be noted that Table 1 is provided as an example, and differentencoding may used.

TABLE 1 Bits b₉b₈b₇ NPD 000 1 001 2 010 3 011 4 100 5 101 6 110 7 111 8

FIG. 9 shows an example MAC frame format for ACK from a coordinator 220to a WTRU 210 including NAD and an ACK request subfield set as CTS inaccordance with one embodiment. The NAD 910 may be indicated using thereserved bits (bits 7-9) of the frame control field 610 in the MAC framefor acknowledgement that is sent from the coordinator 220 to the WTRU210. The ACK request subfield in the frame control field specifieswhether an acknowledgment is required from the recipient on receipt of adata or MAC command frame. The coordinator 220 may use the ACK requestsubfield 920 in the frame control field to represent CTS since the ACKframe does not need to be acknowledged. The frame control subfield 920set with CTS=1 notifies the WTRU that it may start to transmit NPD dataframes without using CSMA/CA. Table 2 shows an example encoding of thebits for NAD in accordance with one embodiment. It should be noted thatTable 2 is provided as an example, and different encoding may used.

TABLE 2 Bits b₉b₈b₇ NAD 000 1 001 2 010 3 011 4 100 5 101 6 110 7 111 8

FIG. 10 is a signaling diagram of an example process of transmittingdata from a coordinator to a WTRU in accordance with one embodiment. AWTRU 210 sends a data request to a coordinator 220 (1002). The WTRU mayinclude a length of active time interval (LATI) in the data requestframe indicating the time period that the WTRU will be active. Thecoordinator 220 acknowledges successful reception of the data request bysending an ACK frame with a number of pending and approved data frame(NPAD) available (1004). The coordinator 220 may set the ACK request bit616 in the frame control field in the ACK frame to ‘1’ (i.e., indicatingCTS) to announce the start of continuous transmission. The coordinatormay determine the NPAD based on the LATI information (if included),fairness, the amount of data pending for the WTRU, and otherconsiderations.

The coordinator 220 sends data frames using continuous transmission modeuntil all NPAD packets are transmitted (1006). For each received dataframe, the WTRU 210 may send back an ACK frame with CTS=1 and LATIreduced accordingly, if included (1008). The coordinator may send thelast frame with NPAD=0 (1010). For the acknowledgement to the last data(NPAD=0), the WTRU 210 may set CTS to ‘0,’ which implies the ending ofthe continuous transmission (1012).

FIG. 11 shows an example format of a data request frame sent from a WTRUto a coordinator with LATI in accordance with one embodiment. The WTRU210 may utilize the frame pending field 1102 (bit 4) and the reservedbits 1104 (bits 7-9) in the frame control field (i.e., total 4 bits) toencode the LATI, if signaled. With four bits, sixteen LATI values orLATI ranges may be supported. Table 3 shows an example encoding of theLATI with the frame pending field 1102 and the reserved bits 1104 in theframe control field. It should be noted that Table 3 is provided as anexample, and different encoding may used.

TABLE 3 Extra Info and Frame Pending Bits b₉b₈b₇b₄ LATI 0000 1 0001 20010 3 0011 4 0100 5 0101 6 0110 7 0111 8 1000 9 1001 10 1010 11 1011 121100 13 1101 14 1110 15 1111 16

FIG. 12 shows an example format of an ACK frame transmitted from acoordinator to a WTRU with NPAD and ACK request field set to indicateCTS. The coordinator 220 may use the ACK request field 1202 to representCTS since the ACK frame does not need ACK request. The three reservedbits (bits 7-9) 1204 may be used to encode the NPAD. Table 4 shows anexample encoding of the NPAD. It should be noted that Table 4 isprovided as an example, and different encoding may used.

TABLE 4 Extra Information Bits b₉b₈b₇ NPAD 000 1 001 2 010 3 011 4 100 5101 6 110 7 111 8

FIG. 13 shows an example format of an ACK frame transmitted from a WTRUto a coordinator in accordance with this embodiment. The WTRU 210 mayuse the ACK request field 1302 to encode 1-bit CTS, and the framepending field 1304 and the reserved bits 1306 (bits 7-9) to encode theLATI.

In another embodiment, a new MAC command (referred to as a data requestand ACK (DRACK)) may be defined to exchange information between thecoordinator 220 and the WTRU 210. The new MAC command DRACK may be usedin both directions to transmit information such as NPD and NAD inupstream and LATI and NPAD in downstream.

FIG. 14 is a signaling diagram of an example process of transmittingdata from a WTRU 210 to a coordinator 220 using a DRACK frame inaccordance with one embodiment. A WTRU 210 sends a DRACK frame with NPDto a coordinator 220 (1402), and the coordinator 220 sends a DRACK framewith NAD to the WTRU 210 (1404). Once the WTRU 210 receives the DRACKframe with NAD, the WTRU 210 sends data to the coordinator 220continuously without using CSMA-CA (1406, 1410). The coordinator 220 mayacknowledge receipt of the data frames (1408, 1412).

In FIG. 14, the acknowledgement messages may be sent from thecoordinator 220 to the WTRU 210. The acknowledgement message may berequested by the WTRU 210 in each data message. The WTRU 210 mayindicate in each data message to the coordinator 220 whether the datamessage needs to be acknowledged or not. For example, the WTRU 210 mayindicate the need of acknowledgement in the last data message so thatcoordinator 220 may use send one acknowledgement to acknowledge all datamessages.

FIG. 15 is a signaling diagram of an example process of transmittingdata from a coordinator 220 to a WTRU 210 using a DRACK frame inaccordance with one embodiment. A WTRU 210 sends a DRACK frame to acoordinator 220 (1502). The WTRU 210 may include an LATI in the DRACKframe. The coordinator 220 sends a DRACK frame with NPAD to the WTRU 210(1504). After sending the DRACK frame with NPAD, the coordinator 220sends data to the WTRU 210 continuously without using CSMA-CA (1506,1510). The WTRU 210 may acknowledge receipt of the data frames (1508,1512).

In FIG. 15, the acknowledgement messages may be sent from the WTRU 210to the coordinator 220. The acknowledgement message may be requested bythe coordinator 220 in each data message. The coordinator 220 mayindicate in each data message to the WTRU 210 whether the data messageneeds to be acknowledged or not. For example, the coordinator 220 mayindicate the need of acknowledgement in the last data message so thatWTRU 210 may use send one acknowledgement to acknowledge all datamessages.

As shown in FIGS. 14 and 15, the WTRU 210 or the coordinator 220 maycontinuously transmit packets without using CSMA/CA after exchangingDRACK. The WTRU 210 may send a DRACK frame using unslotted CSMA/CA,while the coordinator 220 may send a DRACK frame without using unslottedCSMA/CA.

FIG. 16 shows an example format of the DRACK frame 1600. The DRACK framemay have the same frame format as the data request command. The DRACKframe 1600 includes a MAC header (MHR) 1610, a command identifier field1620, and an extra information field 1630. The extra information field1630 may carry information such as NPD, NAD, LATI, and NPAD. Forexample, the first two bits (b₀b₁) of the extra information field 1630may be used to indicate the type of information contained in the rest ofthe extra information field 1630 (for example, b₀b₁=00 for NPD, b₀b₁=01for NAD, b₀b₁=10 for LATI, b₀b₁=11 for NPAD). The remaining bits of theextra information field 1630 carries NPD, NAD, LATI, or NPAD. Theencoding of the information included in the extra information field 1630may be based on Tables 1-4.

The continuous data transmission in accordance with the embodimentsdisclosed herein may be enabled and disabled by setting a particular bitin the MAC frame, (e.g., any bit in a MAC header). For example, a thirdbit of the frame type subfield (i.e., b₂) may be set to ‘1’ to enablethe continuous data transmission mechanism and set to ‘0’ to disable thecontinuous data transmission mechanism.

Table 5 shows the values of the frame type subfield currently defined inIEEE 802.15.4-2006. As shown in Table 5, the third bit (b2) is currentlyset to ‘0.’ By setting/unsetting the third bit of the frame type field,the continuous data transmission mechanism may be dynamically enabled ordisabled.

TABLE 5 Frame Type value b₂b₁b₀ Description 000 Beacon 001 Data 010Acknowledgement 011 MAC Command 100-111 Reserved

It should be noted that the embodiments for encoding of the NPD, NAD,LATI, and NPAD disclosed above are provided as an example, and the aboveinformation may be conveyed via any other fields or subfields of the MACframe (MAC header or body) or any frame type and any encoding methodsmay be used.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

What is claimed is:
 1. A method for data transmissions in a wirelessnetwork, the method comprising: a first device obtaining a firsttransmit opportunity (TxOP) via a contention-based channel accessprocedure; the first device transmitting a first frame to a seconddevice during the first TxOP, wherein the first frame includesinformation regarding a number of pending data frames (NPD) to betransmitted from the first device to the second device; the first devicereceiving an acknowledgement (ACK) frame in response to the first frame,wherein the ACK frame indicates an end of the first TxOP and includesinformation regarding a number of approved data frames (NAD) fortransmission from the first device to the second device; and the firstdevice transmitting a plurality of data frames without performing thecontention-based channel access procedure for obtaining a second TxOP inresponse to the ACK frame.
 2. The method of claim 1, wherein the NAD isequal to or smaller than the NPD.
 3. The method of claim 1, wherein theNAD is determined based on a factor including at least one of fairnessamong a plurality of devices, service properties, and the NPD.
 4. Themethod of claim 1, wherein the first frame comprises a data request andacknowledgement (DRACK) frame, the ACK frame comprises a DRACK frame, orthe first frame and the ACK frame each comprise a DRACK frame.
 5. Themethod of claim 1, wherein the first device terminates sending theplurality of data frames on a condition that a termination indication isreceived from the second device.
 6. The method of claim 1, wherein thechannel access mechanism is carrier sense multiple access/collisionavoidance (CSMA/CA).
 7. A method for data transmissions in a wirelessnetwork, the method comprising: a first device obtaining a transmitopportunity (TxOP) via a contention-based channel access procedure; thefirst device transmitting a first frame to a second device during theTxOP, wherein the first frame is a request for data frames that arepending at the second device to be transmitted to the first device; thefirst device receiving an acknowledgement (ACK) frame in response to thefirst frame, wherein the ACK frame indicates an end of the TxOP andincludes information regarding a number of pending and approved dataframes (NPAD) for reception by the first device; and the first devicereceiving a plurality of data frames in response to the ACK frame. 8.The method of claim 7, wherein the first frame includes informationregarding a length of active time interval (LATI) of the first device,and the NPAD is based on the LATI.
 9. The method of claim 7, wherein thefirst frame comprises a data request and acknowledgement (DRACK) frame,the ACK frame comprises a DRACK frame, or the first frame and the ACKframe each comprise a DRACK frame.
 10. The method of claim 7, whereinthe ACK frame includes a clear-to-send (CTS) bit indicating a channelreservation for the second device for transmission of the plurality ofdata frames to the first device.
 11. The method of claim 7, wherein thefirst device sends a termination indication to the second deviceindicating that the second device should terminate sending the pluralityof data frames.
 12. The method of claim 7, wherein the channel accessmechanism is carrier sense multiple access/collision avoidance(CSMA/CA).
 13. A device for data transmissions in a wireless network,the device comprising: a receiver configured to obtain a first transmitopportunity (TxOP) via a contention-based channel access procedure; atransmitter configured to transmit a first frame to a second deviceusing the first TxOP, wherein the first frame includes informationregarding a number of pending data frames (NPD) to be transmitted to thesecond device; the receiver further configured to receive anacknowledgement (ACK) frame in response to the first frame, wherein theACK frame indicates an end of the first TxOP and includes informationregarding a number of approved data frames (NAD) for transmission fromthe first device to the second device; and a transmitter configured totransmit a plurality of data frames without performing thecontention-based channel access procedure for obtaining a second TxOP inresponse to the ACK frame.
 14. The device of claim 13, wherein the firstframe comprises a data request and acknowledgement (DRACK) frame, theACK frame comprises a DRACK frame, or the first frame and the ACK frameeach comprise a DRACK frame.
 15. The device of claim 13, wherein thefirst device terminates sending the plurality of data frames on acondition that a termination indication is received from the seconddevice.
 16. The device of claim 13, wherein the channel access mechanismis carrier sense multiple access/collision avoidance (CSMA/CA).
 17. Adevice for data transmissions in a wireless network, the devicecomprising: a receiver configured to obtain a transmit opportunity(TxOP) via a contention-based channel access procedure; a transmitterconfigured to transmit a first frame to a second device using the TxOP,wherein the first frame is a request for data frames that are pending atthe second device to be transmitted to the first device; the receiverfurther configured to receive an acknowledgement (ACK) frame in responseto the first frame, wherein the ACK frame indicates an end of the TxOPand includes information regarding a number of pending and approved dataframes (NPAD) for transmission to the first device, and receive aplurality of data frames in response to the ACK frame.
 18. The device ofclaim 17, wherein the first frame includes information regarding alength of active time interval (LATI) of the first device, and the NPADis based on the LATI.
 19. The device of claim 17, wherein the firstframe comprises a data request and acknowledgement (DRACK) frame, theACK frame comprises a DRACK frame, or the first frame and the ACK frameeach comprise a DRACK frame.
 20. The device of claim 17, wherein thefirst device sends a termination indication to the second deviceindicating that the second device should terminate sending the pluralityof data frames.